Reliable predictions indicate that there will be over 300 million cellular phone customers by the year 2000. In the U.S., cellular service is offered not only by dedicated cellular service providers, but also by the regional Bell companies, such as U.S. West, Bell Atlantic and Southwestern Bell, and the national long distance companies, such as AT&T and Sprint. The enhanced competition has driven the price of cellular service down to the point where it is affordable to a large segment of the population.
Wireless subscribers use a wide variety of wireless devices, including cellular phones, personal communication services (PCS) devices, and wireless modem-equipped personal computer (PCs), among others. The large number of subscribers and the many applications for wireless communications have created a heavy subscriber demand for RF bandwidth. To maximize usage of the available bandwidth, a number of multiple access technologies have been implemented to allow more than one subscriber to communicate simultaneously with each base transceiver station (BTS) in a wireless system. These multiple access technologies include time division multiple access (TDMA), frequency division multiple access (FDMA), and code division multiple access (CDMA). These technologies assign each system subscriber to a specific traffic channel that transmits and receives subscriber voice/data signals via a selected time slot, a selected frequency, a selected unique code, or a combination thereof.
To further maximize frequency reuse, wireless carriers frequently implement smaller cells, sometimes referred to as "microcells" or "picocells." The base transceiver station in a microcell (or picocell) broadcasts at relatively lower power over a smaller geographical regions, so that cells may be packed tighter together. This requires a greater amount of infrastructure equipment, but a greater number of subscribers to be serviced by the entire wireless network.
A base transceiver station in a wireless network contains numerous standard-commodity digital processors, such as the MPC860 PowerQUICC.TM. from Motorola, that process the calls being handled by the base transceiver station. The digital processors establish, maintain, and terminate wireless connections between mobile stations (i.e., cell phones, PCS devices, wireless PCs, pagers, etc.) used by subscribers and the wireless network. The digital processors contain hardware communication ports that are used in the process of transmitting and receiving data in the base transceiver station. The communication ports are in turn controlled by internal registers, called buffer descriptors, which set up the communication ports. These registers form a buffer descriptor array that may be used to store status and control information about the communication ports and the data being communicated.
The status and control information is used for both the transmission and the reception of data. This status and control information includes 1) the starting address of the data buffer holding the needed data, 2) the length of the data in the data buffer and 3) bits that may be used to activate and deactivate the digital processor or to indicate certain conditions, including errors.
However, the architecture of digital processors provide only a relatively limited number of registers to be used as buffer descriptors. Since the buffer descriptors are used to control communication ports, and the communication ports control the number of calls handled by the base transceiver station, any limitation on the size of the buffer descriptor array also limits the throughput of the base transceiver station. If the transmitter buffer descriptors of a digital processor are filled when additional data packets are available for processing and transmission, the additional packet processing must wait until a transmitter buffer descriptor becomes available to store them. On the receiver side, if the receiver buffer descriptors are waiting to transfer data to the transmitter buffer descriptors while the transmitter buffer descriptors are unavailable, then incoming data to the receiver is lost because there are no registers in which to store the newly received data.
There is therefore a need in the art for improved transceiver systems for use in wireless networks. In particular, there is a need for communications systems that are not limited by the hardware design of commercially available communications processors. More particularly, there is a need for communications systems that are able to expand the call handling capabilities of communications processors.